Traditional toilets have a plane of left-right symmetry, or an approximate plane of symmetry oriented vertically from the front of the toilet to the back. The P-trap style trapway or drain in a traditional toilet functions like a siphon in removing waste from a toilet bowl. The trapway remains substantially in the plane and therefore requires bends of differing curvatures to alternately form a trap and return water to the sewer. Due to the symmetry constraint, the flush jet typically enters the bowl from either the front or the back and vice-versa for the water exiting the bowl. Toilet drains utilizing a liquid P-trap style trapway typically comprise multiple bends, exiting the sump portion of the toilet bowl in a U-shape and following a course in a single vertical plane extending through the middle of the toilet from front to back. The bend in the drain creates a pipe section angled upwards to trap a column of water and isolate the sewer from the toilet bowl or sink. The pipe then bends over and back down again and empties into the sewer. From a side view, if the first bend has a positive curvature (bends up), the second bend has a negative curvature (bends down).
In a toilet, a water jet from a pressure source such as a tank or wall may enter the toilet bowl near the bottom. Water may also enter the bowl from the rim or another source of rinse water. One goal of low volume flush toilet design with a siphon flush is to fill the trapway completely with water as fast as possible, to “kick” or engage the siphon with minimal water. The higher the velocity of water, the lower volume flush is possible. In order to generate the kick, the siphon water enters the trapway faster than it is leaving. One possible way to implement such a strategy is to increase the resistance of the pipe section after the second bend, by corrugating the flow or reducing the pipe diameter. Both methods, however, limit the exit flow and increase the likelihood of a clog, in addition to making the toilet harder to plunge if a blockage does occur.
Accordingly, there is a need for improvements in the design of flush systems that rapidly inject water and reduce the incidence of drain clogging.